1. Field of the Invention
This invention relates generally to the field of Fischer-Tropsch synthesis. More specifically, the invention relates to a system and method for converting syngas to hydrocarbons via Fischer-Tropsch synthesis. The system and method involve at least two slurry loops comprising at least one magnetic dynamic settling vessel or three or more slurry loops for separating catalyst slurry from gaseous and liquid Fischer-Tropsch products. The slurry loops are in fluid communication with the Fischer-Tropsch reactor.
2. Background of the Invention
Natural gas, coal deposits, and biomass are abundant energy sources that often serve as fuel for a large number of daily uses including heating and power generation. While abundant, the location of these deposits far from industrialized, commercial infrastructure represents a significant hurdle to increased application as a replacement for oil distillates. Additionally, natural gas must be converted to a liquid by an expensive and energy intensive process. Comparatively, as solids coal and biomass have substantial mass for their energetic yield, requiring special tools, packaging and carriers to transport them.
Liquid fuels that are easily transported long distances without expensive processes or packaging are highly advantageous. However, current petroleum exploration and production are unable to keep up with global demands for fuel. This trend is not predicted to change in the future. Resultantly, oil reserves are being depleted despite the rising costs to the end consumer. For this reason increased attention, interest, and investment go into developing technologies that convert solid or gaseous fuels into liquid fuels.
The process of converting the available material to a liquid fuel involves the partial oxidation of the material prior to a catalyzed reaction to create a liquid fuel. The Fischer-Tropsch (FT) reactors contain the vital step of catalyzed synthesis of synthetic petroleum substitute liquid fuels. The process occurs via a catalyzed chemical reaction in which carbon monoxide and hydrogen from the material are converted into liquid hydrocarbons. The reaction is highly exothermic, and requires a cooled reactor to maintain conditions favorable for continued synthesis. Commercial FT reactors require cooling liquid to be transported through heat exchanging conduits in order to remove heat from the reactor.
Additionally, the desirable liquid or wax product must be separated from the catalyst, intermediate hydrocarbon, and associated gases in the reaction slurry which may be returned to the reactor. Current reactor systems use a number of processes in this separation step including filtering, and settling. The process of filtering the solid material and wax from the reaction slurry requires a high energy investment, however, as the mixture must be continuously pumped (circulated) through the system at a rate exceeding the product draw rate. Additionally, maintenance and cleaning of these systems requires stopping the reactor processes completely.
Settlers are a highly preferred method of separation. While comparatively a lower maintenance method of separation, they are highly dependent on the size, shape, and consistency of the solid catalyst particles. Longer time periods, or multiple steps in series or parallel are often required to fully separate the liquid fuel. The number of these devices dictates the rate at which the reactor can produce suitable synthetic products for further processing.
Consequently, there is a need for a commercial FT reactor design that maximizes reactor run time, and efficiency in separating synthetic liquid products from reaction catalyst slurry by incorporating multiple slurry loops and a large slurry bed FT reactor.